Deciphering S-RNase Allele Patterns in Cultivated and Wild Accessions of Italian Pear Germplasm

Management of genetic erosion: The (successful) case study of the pear (Pyrus communis L.) germplasm of the Lazio region (Italy)

Pyrus communis L. is an important temperate fruit with high nutritional and economic value. Italy, as the largest pear producer in the EU and second in the world, has a particularly rich germplasm characterized by hundreds of local varieties. The Lazio Region was the first Italian region to start programs focused on safeguarding varieties at risk of extinction and has started a massive census of fruit varieties by combining molecular data and productive-territorial information. In this study, 311 pear accessions collected from the five provinces of the Lazio region were genetically characterized by the means of nine simple sequence repeat (SSR) markers, eight of which were recommended by the European Cooperative Programme for Plant Genetic Resources (ECPGR). The SSR analysis revealed 250 unique genotypes and 14 cases of synonymies, namely, accessions with different names but identical molecular profiles (100% genetic similarity). The microsatellite set showed a high polymorphism information content (PIC; mean PIC=0.77) and an exceptionally high discrimination power (DP = 0.99), making it particularly efficient both for the study of genetic diversity and for the prediction of the degree of ploidy. Notably, 20% of the accessions displayed triallelic profiles (i.e., accessions having ≥2 loci with a third allele), while the remaining accessions were diploids. These results were further confirmed by flow cytometry data analysis. Standardization of the molecular analyses at the national and international levels and harmonization of the SSR sets used for germplasm characterization are of paramount importance for producing molecular profiles useful for registration and variety maintenance.

Assessment of Chilling Requirement and Threshold Temperature of a Low Chill Pear (Pyrus communis L.) Germplasm in the Mediterranean Area

In temperate climates, bud break and shoot and flower emission of deciduous fruit tree species are regulated by precise chilling and heating requirements. To investigate this aspect, sixty-one accessions of European pear (Pyrus communis L.) collected in Sicily were phenotyped for three consecutive years for harvest date, bud sprouting and blooming to determine both the chilling requirements and the threshold temperature using the Chill Days model. The whole germplasm collection was grown in two different experimental fields located at 10 and 850 m above sea level representing two Mediterranean-type climates in which pear is commonly cultivated. Results revealed a mean threshold temperature of 6.70 and 8.10 °C for the two experimental fields, respectively, with a mean chilling requirement ranging from −103 and −120 days. Through this approach, novel insights were gained on the differences in chilling requirement for early flowering cultivars to overcome dormancy. Furthermore, to better dissect differences in chilling requirement between accessions, the sprouting bud rate of six cultivars was assessed on excised twigs stored at 4 ± 0.1 °C from 300 to 900 h followed by a period at 25 ± 0.1 °C varying from seven to twenty-eight days. Results of both experiments highlighted that Sicilian pear germplasm is characterized by a low chilling requirement compared to other pear germplasm, making Sicilian local accessions valuable candidates to be used for selecting novel cultivars, coupling their low chilling requirements with other traits of agronomical interest.

Phenotypic assessment of pear varieties in mutual pollination

The self-fertility and cross-fertility of pear varieties have been studied in the conditions of the of the Krasnodar region. It was established that most of the not varieties are self-fertile. The varieties are distinguished: Ladozhskaya, Malyshka and Talgar beauty, with partial self-fertility, in which a low percentage of fruit set and its fluctuation over the years are noted. Based on the pollination performed and the analysis carried out, good and acceptable pollinators for promising pear varieties were selected. It has been established that in order to form full-fledged seeds in the fruit of the pear, a full cross-pollination with good pollinators is necessary. The possibilities of individual varieties (a high percentage of fruit tying) with mutual pollination are presented. The analysis of the negative influence of technogenic factors during flowering on the inter-pollination of varieties has been carried out. Cross-pollinated varieties have a narrow selective ability to pollinate varieties, which varies over the years and depends on the growing conditions. Proved the need, when laying gardens correctly choose varieties-pollinators in order to increase the yield of varieties. According to the research results, a self-fertile variety Iyulskaya early was identified. The best pollinators were selected for promising pear varieties for the conditions of the Kuban.